1. Field of the Invention
The present invention relates to a semiconductor device having a multi-layered interconnection structure as well as a method for manufacturing the same, which is employed to form, over a semiconductor structure, a passivation film or a inorganic insulating interlayer of a composite inorganic/organic insulating structure having a composite inorganic, organic insulating interlayer.
2. Description of the Related Art
A conventional insulating interlayer structure will be explained below in connection with the process of forming an inorganic insulating film as a passivation film over a composite organic/inorganic insulating layer structure, by referring to FIG. 2.
First, 1.0 .mu.m-thick plasma SiN film 13 (hereinafter referred to as a P-SiN) is deposited by a plasma CVD method on first interconnection layer 12 (1.0 .mu.m-thick Al-Si layer) of a predetermined pattern formed on a thermal SiO.sub.2 -carried semiconductor substrate and then a through-hole A of a predetermined pattern is formed in the surface portion of the resultant structure by virtue of an ordinary photolithography and RIE (reactive ion etching) methods. A second through-hole of a predetermined pattern is formed by virtue of the ordinary photolithography and RIE methods on the structure subsequent to the coating of polyimide resin 14 and a predetermined heat treatment. Then second interconnection layer 15 (Al-Si 10 .mu.m-thick) of a predetermined pattern is formed by the ordinary sputtering, photolithography and RIE methods. After a sintering step, 1.0 .mu.m-thick P-SiN layer 16 is formed as a passivation film and pad opening 18 is formed by the ordinary photolithography and CDE (chemical dry etching) methods. After eliminating the photo-resist, a semiconductor device is completed which has a conventional multi-layered interconnection structure-see FIG. 2(b) FIG. 2(c) is a plan view where 17 denotes a dicing line and 19 shows cracks in inorganic insulating film 16 for passivation.
The composite interlayer of organic insulating film 14 and inorganic insulating film 13 has the advantages of being easier-to-handle in process, less in an electrical variation, higher in breakdown voltage and lower in cost. On the other hand, inorganic passivation film 16 is excellent in the resistance to humidity, as well as in the mechanical strength, as well known in the art. For this reason, a greater number of semiconductor devices have been manufactured which adopt a combination of the composite interlayer and inorganic passivation film
When, after the assembly of the conventional combination type semiconductor structure, it is incorporated into an associated circuit board, a thermal shock test is conducted at which time a sample is quickly heated at 280.degree. for 30 seconds, followed by a PCT step at 2.5 atmospheres at 127.degree. C. for 20 hours. It has been found that 10% of samples tested are bad in a corrosion mode. In this connection reference is invited to FIG. 3. Here, PCT is a forced humidity-resistance test using pressure and temperature. By the term "corrosion" is meant the corrosion of an interconnection layer due to, for example, water.
Corrosion occurs all at pad site 18. This is due to a stress responsible for the inorganic passivation film, per se, at the pad site and to a stress responsible for the mold resin, as set out below. That is, inorganic passivation film 16 is formed on organic insulating film 14 and, upon the application of stress thereto, readily moved in the direction of a force applied. Since pad site 18 at the boundary of a pattern-free field area is moved by such a force to a greater extent, greater deformation occurs at the metal area of pad site 18 and cracks 19 occur at inorganic passivation film 16 with which the pad site is covered.